He may have headed one of the smallest countries in the European Union but the resignation of Luxembourg’s prime minister Jean-Claude Juncker has caused a stir throughout Europe. Mr Juncker has led his country for 18 years, making him the longest-serving leader in the EU, but it is for his work in Brussels that he has become best known.

Mr Juncker, who also served as finance minister until 2009, led the group of 17 eurozone finance ministers between 2005 and 2012, becoming one of the key faces of the eurozone crisis. His links with the European Union go back further. Staunchly pro-European, he was one of the signatories of the Maastricht Treaty, which paved the way for the single currency, and he played a crucial role as mediator between France and Germany during negotiations on a number of pacts.

Having assumed the position of prime minister in 1995 when Jacques Santer was appointed president of the European Commission, Mr Juncker was himself tipped as a candidate a decade later. He was also a favourite for the position of the first president of the European Council four years ago, a job that eventually went to the then Belgian prime minister, Herman Van Rompuy.

RumoursWhile Mr Juncker dismissed rumours he would be seeking the position of European Commission head next year , a position in Brussels would be an obvious next step for a man who faces the biggest political crisis of his career.

Ironically, it was Juncker’s deep affinity with the EU that led to his undoing — for years he has been criticised by the Opposition for prioritising Europe at the expense of his own country.

Mr Juncker told the parliament on Wednesday that keeping an eye on Luxembourg’s intelligence service had not been his “top priority”.

Ultimately it seems Mr Juncker and his coalition partners had very different ideas about what a prime minister’s role should be, a tension that contributed to the fall of the government.